The pilot overflew the unimproved mountain airstrip in preparation for landing. The pilot reported that the windsock appeared to indicate a calm wind or very little tail wind. The pilot stated that the airplane did not touchdown until 2/3 of the way down the runway. The airplane subsequently exited the far end of the runway, impacting rough terrain and trees, resulting in substantial damage to the airplane and minor injuries to occupants. Examination of the airplane revealed structural damage to the wings and the fuselage. The pilot reported that there were no known mechanical anomalies with the flight control systems, and he reported that the left brake was operating at the time of application.